Preparation And Properties Of Hollow Square Silicon Carbide Beam By Extruding

The hollow square silicon carbide beam was extruded by the batch, which was made from high purity silicon carbide powders and contains the assistant raw materials, such as plasticizer, lubricate and emulsifier to improve the production efficiency and the properties of products. The plasticity of the batch, density of the green bodies, strength and microstructure of the beam had been systematically analyzed using home-developed plastometer, home-developed extrusion force detector, Archimedes law, universal testing machine and SEM, respectly.The effect of the content of plasticizer (Hydroxyethyl cellulose (HEC) and phenolic resin), lubricant and emulsifier on plasticity of the batch, extrusion force and density of the green bodies and the effect of the solidifying law on mechanical properties of products were studied in this paper. The results are as follows:(1) The best plastic property was achieved by using 13.5wt% plasticizer,3wt% lubricate and 3wt% emulsifier in the phenolic resin system, the density of the green bodies reached 2.24 g/cm3, the bending strength reached 53MPa; The best plastic property was achieved by using 4wt% plasticizer and 20wt% water in the HEC system, the density of the green bodies reached 2.14 g/cm3, the bending strength reached 50.5MPa.(2) For the phenolic resin system, when the green bodies were solidified with the heating up speed of 4℃/h to 175℃(43.75h), the products can be sintered steadily at 1905℃for 30min under Nitrogen atmosphere. Under above parameters, its density was 3.11 g/cm3, bending strength was 320MPa. For the HEC system, the adequate drying time was 72h at the constant temperature and humidity environment, when sintered at 1905℃for 30min under Nitrogen atmosphere, its density was 3.06 g/cm3, and bending strength was 310MPa.(3) Compared the phenolic resin system (10.8wt%) with the HEC system (26wt%) the content of free silicon in the silicon carbide beam, the former was few, and shows that the phenolic resin system can prominently improve the high temperature property of silicon carbide beam. (4) Compared the phenolic resin system with the HEC system, the phenolic resin system can significantly improve the production efficiency and properties, such as the density, strength and microscopic structure.(5) Compared extrusion with the slip casting, the extrusion can significantly improve the production efficiency and properties. With the extrusion technique, the production efficiency increased 8 times, the drying rate increased 1.5 times, the density (3.11g/cm3) and the bending strength (296 MPa) are higher than the slip casting.